Massed but not spaced training impairs spatial memory

The Morris water maze and the object displacement task are two popular tools used to investigate spatial learning and memory. Research has focused mainly on the acquisition of spatial tasks while little attention has been given to the retention phase. We examined the effects of different training procedures on retention of the water maze and also reactivity to spatial change in the object displacement task 7 days post-acquisition. We found that massed-trained animals were impaired on retention of the water maze compared to those animals that had received spaced-training. We also found that the massed-trained animals habituated readily to their environment in the object displacement task while the spaced-trained group did not. Furthermore the massed-trained group did not react to spatial change 7 days post-habituation compared to the increased reactivity displayed by the spaced-trained group. Results are discussed in terms of poor encoding of the environment leading to poor retention. (C) 2002 Elsevier Science B.V. All rights reserved.